Wumpus Posted November 27 Share Posted November 27 Hello Buildhub, I need your experience please. Theres a bit of a story to go with this, so bear with me. We completed our house last year and have been living here for over 18 months. The house is built to Passivhaus principles - air tightness tested at 0.38, insulation is great with floor 0.09, roof 0.1 and walls 0.13. Triple glazed throughout (Norrsken, very happy), MVHR at 86%, thermal bridges minimised. We did not complete a PHPP but do have detailed heat loss calculations for each room. As funds got a bit tight, we didn’t put in the ASHP we planned, and instead put in an electric flow boiler which feeds our lower floor UFH, and we have a direct electric cylinder. Maybe this was a mistake, no point go in back over it. The house is performing exceptionally well. We batch heat the lower floor slab overnight in Intelligent Octopus GO hours, and typically the requirement is 10-15kWh a day. We don’t really top it up during the day except when very cold outside, which is not very often in Devon. The internal temperature loss is around 1 to 1.5 degrees a day and we maintain the lower floor between 20 and 22 degrees (heat to 21.5 overnight). All of our heat for the last 12 months (2600 kWh) cost us £191, which I think is pretty good. Hot water (4100 kWh) about £340 a year, again overnight. All this points to an ASHP being of marginal value, we won’t save much on £530 a year and need to add in annual servicing. At a COP of 3, we might save £350 a year on the electricity? This would all be “case closed” if it were not for our mortgage, which is with Ecology (who are fantastic). Ecology offer a discount for achieving a B or higher SAP on the as-built building. Our SAP as designed was A101, our as-built is C79. The only difference is the change from ASHP to electric boiler, everything on the SAP certificate is “very good” except for heating and hot water, which are “very poor”. Our insulation levels exceed the as-designed SAP numbers. We could spend some time discussing how SAP does not do a great job for houses like ours, but again not much value here. So, I had an MCS certified contractor around to look at replacing the electric boiler. He pretty much understood that we have a house with very low heat loss, but old me that he had to install heat emitters in every habitable room. We don’t have UFH or radiators on the upper floor, and adding them would add a lot of cost and make quite a mess of the house. Any advice or experience from anyone on whether it’s is an MCS requirement to have heat emitters in every room, or any other thoughts on how to proceed? The mortgage discount is worth doing if the costs are less than £2500 including the government grant. Thanks all 1 Link to comment Share on other sites More sharing options...
mike2016 Posted November 27 Share Posted November 27 it will cost a lot more to retrofit an A2A / A2W system that you would save on the mortgage switching to a greener rate. Unless you are selling and there is a significant gain to having an A rated home, I'd say continue as you are. See what a heat pump cylinder would cost to install as though that takes longer to heat up the water it is much more efficient (heat pump is built into the top of the cylinder and needs two vents to outside). That might improve the SAP enough but will save you more money on hot water heating, best return? Link to comment Share on other sites More sharing options...
Conor Posted November 27 Share Posted November 27 Why are you with ecology and not a residential mortgage company if you have completed works? You'll get a much better rate, at least 1.5% lower. Link to comment Share on other sites More sharing options...
Wumpus Posted November 27 Author Share Posted November 27 (edited) 12 minutes ago, Conor said: Why are you with ecology and not a residential mortgage company if you have completed works? You'll get a much better rate, at least 1.5% lower. Fair challenge and this may be the path we go for. I was trying to reduce our CO2 footprint and perhaps enhance value if we sell in the future. Of course we could remortgage as well. Edited November 27 by Wumpus Link to comment Share on other sites More sharing options...
JohnMo Posted November 27 Share Posted November 27 23 minutes ago, Wumpus said: 10-15kWh a day So if you have 7 hrs of cheap electric, that's about 2kW per HR to charge the floor, plus an allowance for DHW heating. I would do it my self. A very basic heat pump set flow temp. Your floor is a buffer, charge as you do now, so keep it simple. This lives in the house so you need two holes in the wall. It's a fixed flow temp, super simple, which is all you really need. Don't bother with the grant. https://www.theheatpumpwarehouse.co.uk/shop/heat-pumps/trianco-activair-indoor-heatpump-3kw/ 1 Link to comment Share on other sites More sharing options...
JoeBano Posted November 27 Share Posted November 27 29 minutes ago, JohnMo said: So if you have 7 hrs of cheap electric, that's about 2kW per HR to charge the floor, plus an allowance for DHW heating. I would do it my self. A very basic heat pump set flow temp. Your floor is a buffer, charge as you do now, so keep it simple. This lives in the house so you need two holes in the wall. It's a fixed flow temp, super simple, which is all you really need. Don't bother with the grant. https://www.theheatpumpwarehouse.co.uk/shop/heat-pumps/trianco-activair-indoor-heatpump-3kw/ I’m guessing you are not messing about with permitted planning with this? Link to comment Share on other sites More sharing options...
JohnMo Posted November 27 Share Posted November 27 7 minutes ago, JoeBano said: permitted planning It's not required, there is no outside unit. Nor is any planning permission. Link to comment Share on other sites More sharing options...
Russdl Posted November 27 Share Posted November 27 55 minutes ago, JohnMo said: This lives in the house so you need two holes in the wall. It's a fixed flow temp, super simple, which is all you really need. Don't bother with the grant. They look clever/very simple and probably ideal for a low energy house. What are the negatives? Just the relatively low output? Link to comment Share on other sites More sharing options...
Wumpus Posted November 27 Author Share Posted November 27 1 hour ago, JohnMo said: So if you have 7 hrs of cheap electric, that's about 2kW per HR to charge the floor, plus an allowance for DHW heating. I would do it my self. A very basic heat pump set flow temp. Your floor is a buffer, charge as you do now, so keep it simple. This lives in the house so you need two holes in the wall. It's a fixed flow temp, super simple, which is all you really need. Don't bother with the grant. https://www.theheatpumpwarehouse.co.uk/shop/heat-pumps/trianco-activair-indoor-heatpump-3kw/ I like this idea. I would need my plumber back as I certainly don’t trust my abilities in that direction, but the rest is very possible. There is intello fabric on the wall where our MVHR ducting exits, so I guess just adjacent to that and good taping to keep everything airtight. Thanks Link to comment Share on other sites More sharing options...
JohnMo Posted November 27 Share Posted November 27 7 minutes ago, Russdl said: What are the negatives? Fixed speed, little or no modulation. But ideal for batch charging the floor as the OP does. Would I bother connecting to DHW? You may be better setting to 35 to 40 degs. 1 Link to comment Share on other sites More sharing options...
JoeBano Posted November 27 Share Posted November 27 42 minutes ago, JohnMo said: It's not required, there is no outside unit. Nor is any planning permission. Shame I have a 6kw heat loss. Link to comment Share on other sites More sharing options...
Wumpus Posted November 27 Author Share Posted November 27 (edited) 25 minutes ago, JohnMo said: Fixed speed, little or no modulation This could be tricky, the bigger return on investment is on DHW. Our UFH flow temperature is 35 degrees, but that wouldn’t make a dent in the hot water? Edited November 27 by Wumpus Link to comment Share on other sites More sharing options...
JohnMo Posted November 27 Share Posted November 27 9 minutes ago, Wumpus said: This could be tricky, the bigger return on investment is on DHW. Our UFH flow temperature is 35 degrees, but that wouldn’t make a dent in the hot water? Have a read of the manual, it shows various schemes. Go the link I left and scroll down Link to comment Share on other sites More sharing options...
JoeBano Posted November 27 Share Posted November 27 They just released 5kw and 7kw versions but at £7000… Think it’s a very good idea. Link to comment Share on other sites More sharing options...
mk1_man Posted November 27 Share Posted November 27 Hi, we are in middle of a deep refit of 1960's house 250m2, triple glazed, good levels of insulation, dug out floors retrofitted with ufh (best thing we ever did) and initially ran on a Viessmann boiler. This summer I replaced it with a Vaillant Arotherm plus 7kW. The route I took after getting multiple quotes was to purchase kit and install myself but claim the £7.5k grant via umbrella mcs company. This route worked great for us and made the install cost neutral. The money we saved was placed into 25 kWh of battery storage running via a Sunsynk 5.5kWh inverter (solar still to be installed) now running the house 24 x 7 @ 5p kWh (Tomato Energy) and couldn't be happier. 1 Link to comment Share on other sites More sharing options...
Wumpus Posted November 27 Author Share Posted November 27 1 hour ago, mk1_man said: The route I took after getting multiple quotes was to purchase kit and install myself but claim the £7.5k grant via umbrella mcs company This sounds great. Can you recommend the company? Link to comment Share on other sites More sharing options...
mk1_man Posted November 27 Share Posted November 27 https://www.air2heat.co.uk/mcs-umbrella-scheme Paul was fantastic throughout. 1 Link to comment Share on other sites More sharing options...
MikeSharp01 Posted November 27 Share Posted November 27 6 hours ago, Wumpus said: Our SAP as designed was A101, our as-built is C79. Yes this is down to direct electric heating it's the dumbest thing ever isn't it. Link to comment Share on other sites More sharing options...
ringi Posted November 29 Share Posted November 29 The incoming changes to EPC includes using measured airtightness if you provide the results. It maybe enough to get past the EPC tickbox. Adding PV can also get EPC points. Link to comment Share on other sites More sharing options...
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